The reinforcement of rock originally involved the use of passive support systems that utilised timber and steel structural supports. Active support systems were subsequently developed including the provision of relatively rigid roof bolts which have been widely used and still find application. Early roof bolts were provided with mechanically operated wedge devices to facilitate anchorage of the roof bolts in the relevant rock. Later, concrete grout and chemical anchoring materials were developed for anchorage of roof bolts. Most recently, flexible wire tendons with a length of between six to twelve meters and which are commonly used with such anchoring materials have found widespread application.
To install such a wire tendon, the bore for receipt of the tendon is first drilled into the rock to be supported. Given the length of the tendon it is common to use a number of drill rod extensions to obtain the required bore depth. The selected anchoring material is then inserted in the bore and the wire tendon manually or mechanically driven into the bore prior to being tensioned to thereby support the rock once it has been anchored in position by the anchoring material.
The anchoring material is typically contained in cartridges which facilitates its insertion into the drilled bore. The material exists in the cartridges as separate adhesive and catalyst components which are mixed together by the tendon when inserted in the bore to cause the anchoring material to set and so anchor the tendon in position.
To date, however, the amount of anchoring material used has been limited such that only up to about three meters of tendon length is encapsulated by the material resulting in less than optimal anchorage of the tendon and support of the rock.
The encapsulation length of the tendons has been restricted due to the inability to drive a tendon into long lengths of highly viscous cartridges while at the same time rotating the tendon to mix the anchoring material the cartridges contain.
More particularly, while portable pneumatic bolters are available for rotating a wire tendon while driving it into a predrilled bore in the roof of a mine for example, use of such machines involves exerting the drive and rotational forces on the trailing end of the tendon. When a substantial length of the tendon protrudes from the bore and is unable to be readily inserted further as in the case where the bore is filled with several meters of cartridges containing anchoring material, the application of the drive force to the trailing end of the tendon causes the tendon to flex while being rotated which is highly undesirable as it presents a safety risk to the user of the apparatus and anyone in the immediate vicinity of the apparatus.
Machines with adjacent rotating thrust wheels adapted to grip a flexible tendon between them and so drive the tendon into a predrilled bore are also known. However, such apparatus do not have the capacity to rotate the tendon while driving it into the bore as is required when anchoring material comprising separate adhesive and catalyst components is to be used. Moreover, the grip provided by the apparatus is inadequate to readily thrust the tendon through long lengths of adhesive material containing cartridges.
Drilling rigs for drilling bores to a desired depth using a plurality of drill extension rods are also known. However, there remains a need for a method enabling greater encapsulation of long flexible tendons with anchoring material than has been achieved in the past in order to enhance the reinforcement of rock.